Constellation Energy Corp., the biggest US operator of reactors, expects Three Mile Island to go back into service in 2028.

The Three Mile Island Nuclear plant, home of the worst nuclear accident in U.S. history, would restart under a deal in which Microsoft purchases all its power.

Constellation Energy has signed a 20-year power purchase agreement with Microsoft that will pave the way for restarting its Three Mile Island nuclear power plant, the utility firm said on Friday.

New nuclear power plants in Georgia have helped flip the state's power mix so that electricity from clean energy sources has exceeded fossil fuel electricity output for the first time.

Software giant Microsoft just struck a deal with Constellation Energy to receive energy from the Three Mile Island nuclear site in Pennsylvania. The agreement means that a unit that was shut down five years ago will be restarted.